Question

As many do I have a config.php file in the root of a web app that I want to include in almost every other php file. So most of them have a line like:

require_once('config.php'); 

or sometimes

require_once('../config.php'); 

or even

require_once('../../config.php'); 

But I never get it right the first time. I can’t figure out what php is going to consider to be the current working directory when reading one of these files. It is apparently not the directory where the file containing the require_once() call is made because I can have two files in the same directory that have different paths for the config.php.

How I have a situation where one path is correct for refreshing the page but an ajax can that updates part of the page requires a different path to the config.php in the require_once() statement;

What’s the secret? From where is that path evaluated?

Shoot, I was afraid this wouldn’t be a common problem – This is occurring under apache 2.2.8 and PHP 5.2.6 running on windows.

Answer 1

The current working directory for PHP is the directory in which the called script file is located. If your files looked like this:

/A    foo.php    tar.php    B/        bar.php 

If you call foo.php (ex: http://example.com/foo.php), the working directory will be /A/. If you call bar.php (ex: http://example.com/B/bar.php), the working directory will be /A/B/.

This is where it gets tricky. Let us say that foo.php is such:

<?php require_once 'B/bar.php'; ?> 

And bar.php is:

<?php require_once 'tar.php'; ?> 

If we call foo.php, then bar.php will successfully call tar.php because tar.php and foo.php are in the same directory which happens to be the working directory. If you instead call bar.php, it will fail.

Generally you will see either in all files:

require_once realpath( dirname( __FILE__ ) ).'/../../path/to/file.php'; 

or with the config file:

// config file define( "APP_ROOT", realpath( dirname( __FILE__ ) ).'/' ); 

with the rest of the files using:

require_once APP_ROOT.'../../path/to/file.php';